Abstract
In this study, crack growth under steady state creep conditions is analysed. A theoretical framework is introduced in which the constitutive behaviour of the bulk material is described by power-law creep. A new class of damage zone models is proposed to model the fracture process ahead of a crack tip, such that the constitutive relation is described by a traction-separation rate law. In particular, simple critical displacement, empirical Kachanov type damage and micromechanical based interface models are used. Using the path independency property of the C^*-integral and dimensional analysis, analytical models are developed for pure mode-I steady-state crack growth in a double cantilever beam specimen (DCB) subjected to constant pure bending moment. A computational framework is then implemented using the Finite Element method. The analytical models are calibrated against detailed Finite Element models. The theoretical framework gives the fundamental form of the model and only a single quantity hat{C}_k needs to be determined from the Finite Element analysis in terms of a dimensionless quantity phi _0, which is the ratio of geometric and material length scales. Further, the validity of the framework is examined by investigating the crack growth response in the limits of small and large phi _0, for which analytical expression can be obtained. We also demonstrate how parameters within the models can be obtained from creep deformation, creep rupture and crack growth experiments.
Highlights
At elevated temperature, creep crack growth (CCG) is one of the most common failure mechanisms in many engineering applications, e.g. structural components, E
The crack propagation scenarios are characterized by the nature of the crack tip fields at these instants: (i) the small-scale creep zone is formed surrounded by the elastic medium, (ii) the primary creep zone is large enough but remains surrounded by the elastic medium, (iii) the secondary creep zone is formed inside the primary creep zone but both zones remain surrounded by the elastic medium, (iv) the secondary creep zone is expanding inside the primary creep zone which dominates, (v) the secondary creep zone dominates
A double cantilever beam specimen (DCB) subjected to constant pure bending moment is studied and analytical models are developed for pure mode-I steady-state crack growth
Summary
Creep crack growth (CCG) is one of the most common failure mechanisms in many engineering applications, e.g. structural components, E. A small-scale creep zone, i.e. small in comparison with the physical characteristic length of the body, is formed in the vicinity of the crack tip. In this stage, the material deforms by primary creep inside the creep zone and remains elastic elsewhere. Thereafter, the primary and secondary creep zones continue to expand at the cost of the elastic and primary zones, respectively. During this process, damage accumulates in the crack tip region, which may lead to crack propagation if a critical condition is met. The crack propagation scenarios are characterized by the nature of the crack tip fields at these instants: (i) the small-scale creep zone is formed surrounded by the elastic medium, (ii) the primary creep zone is large enough but remains surrounded by the elastic medium, (iii) the secondary creep zone is formed inside the primary creep zone but both zones remain surrounded by the elastic medium, (iv) the secondary creep zone is expanding inside the primary creep zone which dominates, (v) the secondary creep zone dominates
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